THE TRAGIC deaths of five patients in a National Institutes of Health (NIH) study of the experimental hepatitis drug fialuridine or fluoroidoarauracil (FIAU) were, given the circumstances, "unavoidable" and due to a wholly new type of unexpected and delayed liver toxicity. There were no noteworthy flaws in the conduct of the study.

This is the conclusion of an exhaustive review of the situation conducted by a subcommittee of the NIH Director's Advisory Committee chaired by David R. Challoner, MD, vice president for health affairs, University of Florida College of Medicine, Gainesville, and David M. Kipnis, MD, distinguished university professor of medicine, Washington University School of Medicine, St Louis, Mo. The inquiry was conducted at the request of NIH Director Harold Varmus, MD, and the report presented at a committee meeting on June 2.

This report, the second to follow the deaths, could be viewed as at variance with an earlier